Method of forming sheet metal panels



Feb. 12, 1963 H. A. FROMSON 3,

. METHOD OF FORMING SHEET METAL PANELS Filed May 10, 1960 2 Sheets-Sheet1 Z6 30 27 .1 -E. J.

f v I A INVENTOR /3 Hon A40 A. Fomsow Feb. '12, 1963 Filed May 10, 1960H. A. FROMSON METHOD OF FORMING SHEET METAL PANELS 2 Sheets-Sheet 2INVENTOR Howe/e0 AFEOMsU/V United States Patent s,e77,es1 MET-MD (llFtERMlh-IG Eil-lEE'l METAL PANELS Howard A. Fromson, Weston, 6min. FiledMay it), rose, Ser. No. 283275 Claims. (Cl. sa -421 The presentinvention relates to a method of forming or erecting sheet metal panelsand relates, more particularly, to a method of forming or erecting asheet metal panel having inflatable portions intermediate its sideedges.

An object of the invention is to provide a method of forming or erectinga sheet metal panel in such a way that the panel is stressed and undertension when it forms of a structure. Another object of the invention isto provide a method of forming or shaping sheet metal panels into avariety of curved structural shapes expeditiously and at low cost.

Other objects of the invention will become apparent and be betterunderstood from the following description and the accompanying drawingsin which:

FIG. 1 is a perspective view of a sheet metal panel as initiallyattached to a structue in accordance with the present invention;

FIG. 2 is a perspective view of the sheet metal panel shown in P16. 1after erection and stressing of the panel in accordance with the presentinvention;

FIG. 3 is a fragmentary view in section taken along line 3-3 of FIG. 1,but on an enlarged scale;

FIG. 4 is a fragmentary view in section taken along line 4- of H6. 2,but on an enlarged scale;

PEG. 5 in assembled condition;

a step in the method of forming a sheet metal panel into a structural.shape of a desired curvature in accordance with the invention;

PEG. 6 is a perspective view of the parts shown in FIG. 5 in assembledcondition;

FIG. 7 is a perspective view illustrating the final step in the formingof a curved panel in accordance with the invention;

PEG. 8 is a section view taken along line 88 of FIG. 7; and

FIG. 9 is a section view taken along line --9 of PEG. 8.

in general, the present invention relates to the erecting or forming ofa sheet metal panel having inflatable portions intermediate its sideedges by inflating said portions, entirely or partially, while the sideedges of the panel are held in fixed positions. As will be describedhereinafter in detail, the panel may be erected in a stressed conditionas part of a structure or it may be formed into a wide variety of curvedstructural shapes.

Referring to the drawings and to H6. 1 in particular, there is a thinsheet metal panel lit which is fastened along its side edges to spacedframe members 11 by rivets 12 or other suitable fastening means.

The panel is formed with a plurality of inflatable portions formed byinternal unbonded surfaces 13 defining internal slits which extendlengthwise of the panel in spaced and generally parallel relation toeach other. However, the inflatable portions do not have to be parallelto each other or the side edges of the panel. Such a panel may be formedby rolling tubes which have con treated internally with a resist intothe surface of a metal sheet as taught in my United States LettersPatent No. 2,828,533 issued April 1, 1958 for Method of Making integralSheet and Tubing Products. However, it will be indcrstood that othermethods of forming the panel may be employed if desired.

As shown in FIGS. 2 and 4, the portions of the panel defining theunbonded internal surfaces 13 may be sep- ICC arated and expanded intomore or less tubular form, as indicated at 14, by introducing fluidunder pressure between said surfaces. When the unbonded internalsurfaces 13 are expanded, the distance between the points A at the endsof such surfaces is reduced, as shown in FIGS. 3 and 4, and this causesa reduction in distance between the edges of the panel as shown in FIG.2.

The inflation is carried out with the side edges of the panel fixed tothe frames, and the reduction in the width of the panel takes up anyslack which may be present in the panel as initially installed on theframes (see FIG. 1), so that the panel, as finally installed, is tightlystretched and is under stress in a direction perpendicular to its sideedges. In addition, the erected panel contains spaced tubular portionswhich not only lend strength and rigidity to the panel, but also providea certain amount of give or stretchability to the panel which canaccommodate transverse stresses or dimensional changes in the frameworkof the structure without rupturing or tearing the panel. For example, ifthe frames are separated by shifting, the tubular portions of the panelwill collapse slightly and assume an elliptical form.

It should be noted that the panel does not have to be rectangular, butcan be triangular or any other desired shape. Also, such a panel can beerected in a curved conformation, as in a domed structure, as well as ina given plane.

In addition to the erection of a metal panel as described above, thepresent invention also permits sheet metal panels to be formed into awide variety of curved shapes prior to installation as part of astructure without the use of expensive presses and shaping dies or thelike. An example of such a procedure is illustrated in in FIGS. 5through 9.

In carrying out such an operation, a sheet metal panel 2,}. havinginflatable portions formed by a series of spaced unbonded internalsurfaces 2?; extending lengthwise thereof, is formed initially with anarched center portion 23 and with flanges 24 extending along oppositesides thereof. Each of the flanges is placed between a pair of rigidclamping strips 2.5, 26 and the panel and the clamping strips are thenattached to flanges 27 extending along opposite sides of a form 28 bymeans of bolts 29 and nuts 36 or other suitable fastening devices whichextend through the flanges and the clamping strips at spaced pointsthroughout their length. This prevents the panel edges from moving whenthe inflatable portions of the panel are expanded.

The center part 31 of the form 28 which underlies the arched center partof the panel, has a raised or con vexly curved surface corresponding tothe curvature to be imparted to the panel. Such a form may be made ofwood, plaster or other suitable material. When the panel has beenattached to the form, as shown in FiG. 6, the inflatable portions of thepanel containing the unbonded internal surfaces 22 are then inflated, asindicated at 32, by the introduction of fluid under pressure between theunbonded surfaces. As explained above, this causes a contraction to takeplace in the width of the panel and such contraction, in this instance,draws the center portion of the panel down tightly against the curvedsurface of the form. When the panel is brought into contact with thesurface of the rigid form, further expansion of the panel due to thepressure of the fluid at the points where such contact is made willcease. Thus, as shown in FIG. 8, the portions 32 of the panel definingthe unbonded internal surfaces may be expanded non-uniformly throughouttheir length. In the form illustrated, the expanded portions of thepanel are opened to a lesser extent toward their remote or high ends,due

3 to the fact that the panel first contacted the curved surface of theform at such remote ends as the expansion took place and that suchcontact progressed toward the near ends of the inflatable portions ofthe panel as the expansion thereof continued.

In addition, as shown in FIG. 9, the expansion of the portions of thepanel defining the unbonded internal surfaces may also be non-uniformacross the width of the panel, depending on the particular curvature ofthe surface of the form. In this connection, it should be noted that itis desirable, although it may not be essential, to inflate or expand theseveral portions defining the unbonded internal surfaces simultaneouslyand under substantially uniform pressure.

Substantially the same result may be obtained by fully inflating orexpanding the portions of the panel defining the unbonded internalsurfaces throughout their length and then drawing the panel down intocontact with the curved surface of the form by means of the clampingstrips. In such a case, the expanded portions will collapse and conformto the shape of the form as the panel contacts the form and they alsopermit the panel to be stretched as they are flattened.

prestressed panel structure composed of frame members fixed in laterallyspaced relation to each other and a sheet metal panel extending betweensaid frame members and having its side edges respectively permanentlysecured to said frame members; comprising the steps of providing framemembers in fixed laterally spaced relation to each other, providing asheet metal panel having elongated inflatable portions intermediate theside edges thereof extending generally lengthwise of said panel,

permanently securing the side edges of said panel to said respectiveframe members, 'and thereafter inflating said inflatable portions untilthe panel is placed in tension between its side edges while maintainingthe fixed spaced relationship of said frame members to complete theprestressed panel structure reinforced by the inflated portions.

2. The method defined in claim 1 wherein said panel is unsupportedbetween said frame members during inflation.

3. The method defined in claim 1 wherein said inflatable portions extendgenerally lengthwise of said frame members.

4. The method defined in claim 3 wherein slack in said panel betweensaid frame members is substantially taken up prior to inflation of saidinflatable portions.

5. The method of forming a reinforced sheet metal panel having a desiredconfiguration; comprising the steps of providing a sheet metal panelhaving elongated inflatable portions intermediate the side edges thereofextending generally lengthwise of said panel, securing the opposite sideedges of said panel in fixed positions at opposite sides of a form suchthat the panel between said side edges bows in a direction away'from acontoured surface of said form, and thereafter inflating said inflatableportions to contract said panel into surface engagement with saidcontoured surface.

References Cited in the file of this patent UNITED STATES PATENTS2,086,134 Ludwick July 6, 1937 2,294,137 Spofford Aug. 25, 19422,662,273 Long Dec. 15, 1953 2,740,188 Simmons Apr. 3, 1956 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,077 ,031February 12, 1963 Howard A, Fromson It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.

Column 1, line 32, for "FIGO 5 in assembled conditiong" read FIG 5 1s anexploded view in perspective illustrating Signed and sealed this 3rd dayof September 1965 (SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

1. THE METHOD OF ERECTING AND FORMING A REINFORCED PRESTRESSED PANELSTRUCTURE COMPOSED OF FRAME MEMBERS FIXED IN LATERALLY SPACED RELATIONTO EACH OTHER AND A SHEET METAL PANEL EXTENDING BETWEEN SAID FRAMEMEMBERS AND HAVING ITS SIDE EDGES RESPECTIVELY PERMANENTLY SECURED TOSAID FRAME MEMBERS; COMPRISING THE STEPS OF PROVIDING FRAME MEMBERS INFIXED LATERALLY SPACED RELATION TO EACH OTHER, PROVIDING A SHEET METALPANEL HAVING ELONGATED INFLATABLE PORTIONS INTERMEDIATE THE SIDE EDGESTHEREOF EXTENDING GENERALLY LENGTHWISE OF SAID PANEL, PERMANENTLYSECURING THE SIDE EDGES OF SAID PANEL TO SAID RESPECTIVE FRAME MEMBERS,AND THEREAFTER INFLATING SAID INFLATABLE PORTIONS UNTIL THE PANEL ISPLACED IN TENSION BETWEEN ITS SIDE EDGES WHILE MAINTAINING THE FIXEDSPACED RELATIONSHIP OF SAID FRAME MEMBERS TO COMPLETE THE PRESTRESSEDPANEL STRUCTURE REINFORCED BY THE INFLATED PORTIONS.